Vibration and shock resistant liquid crystal display and associated methods

ABSTRACT

A liquid crystal display (LCD) includes a first panel assembly and a second panel assembly with a liquid crystal material layer positioned therebetween, and wherein the first panel assembly has a resonant frequency substantially the same as a resonant frequency of the second panel assembly so that the LCD is resistant to damage from vibration. The first panel assembly preferably includes a first cover panel immediately adjacent the liquid crystal material layer and at least one additional panel positioned adjacent the first cover panel Similarly, the second assembly may include a second cover panel immediately adjacent the layer of liquid crystal material and at least one additional panel adjacent the second cover panel. The first panel assembly has substantially matched mechanical properties to the second panel assembly. For example, the substantially matched mechanical properties preferably include a stiffness to mass ratio. In addition, the resonant frequency is preferably a first mode resonant frequency. Accordingly, damage caused by the relative motion between the first and second assemblies is avoided by matching the first and second assemblies. For additional resistance to shocks, each of the assemblies may include a support panel, such as provided by a glass plate A front assembly, may also include at least one filter panel. The LCD may also include a frame mounted around a periphery of the first and second panel assemblies. Preferably, the first panel assembly has a coefficient of thermal expansion substantially the same as a coefficient of thermal expansion of the second panel assembly. For additional comparability, the frame also preferably has a coefficient of thermal expansion substantially the same as the coefficient of thermal expansion of the first and second panel assemblies.

GOVERNMENT LICENSE RIGHTS

The U.S. Government has a paid-up license in this invention and theright in limited circumstances to require the patent owner to licenseothers on reasonable terms as provided for by the terms of contract No.DAAJ09-91-C-A004, subcontract No. KAA005 awarded by the U.S. Army.

FIELD OF THE INVENTION

The present invention relates to the field of displays, and, moreparticularly, to a rugged display for use in severe shock and vibrationenvironments.

BACKGROUND OF THE INVENTION

Liquid crystal displays (LCDs) are widely used to convey information toa user, especially where the information is generated by a computer orprocessor. For example, an LCD is commonly used in a personal computer,a portable data terminal, to display information to a user. An LCD mayalso find use in aircraft and other vehicles that may subject the LCD tosevere shocks or vibration.

An LCD typically includes a pair of opposing glass cover plates with theliquid crystal material positioned between the cover plates. Thisstructure is typically referred to as an LCD sandwich. One or morepolarizing layers may be joined to the glass cover plates for a typicalLCD. Unfortunately, the liquid crystal material may be readily damagedby shock or vibration imparted to the display.

Attempts have been made in the past to ruggedize a conventional LCD tosurvive shocks, such as from dropping and/or vibration. One or moresupporting plates may be joined to the front or back surfaces of the LCDsandwich, as disclosed, for example, in U.S. Pat. No. 5,606,438 toMargalit et al. The patent further discloses a ruggedized LCDincorporating layers of adhesive which extend continuously across thefront and back surfaces of the LCD sandwich. The adhesive layers jointhe LCD sandwich to a front glass plate and a rear diffuser.

The adhesive layer on the front is described as increasing the moment ofinertia of the LCD sandwich by causing the LCD sandwich and front glassto behave as single unit. Accordingly, localized stress is reduced whenthe unit as a whole suddenly decelerates in a drop test, for example. Inaddition, the thickness of the adhesive layer is disclosed as between 4to 20 or 30 microns to thereby allow differential thermal expansionbetween the LCD sandwich and the front glass, for example. Further, thefront glass plate includes edge portions which extend outwardly and arecaptured in a corresponding recess of a plastic mounting frame so thatthe LCD is suspended from the front glass plate carried by the frame.

U.S. Pat. No. 5,150,231 to Iwamoto et al. discloses another approach toruggedizing an LCD. In particular, the patent discloses an LCD panelwhich is mounted to a frame by elastic members. In addition, the framedefines an almost enclosed space behind the LCD which traps air todampen motion and thereby further protect the LCD from dropping orvibration.

Unfortunately, conventional approaches to ruggedizing an LCD may not besuccessful in protecting the relatively delicate liquid crystal materialagainst shock and vibration. This may be so especially in a vehicle,such as an aircraft, which may have severe and sustained vibrationlevels.

Conventional attempts to ruggedize an LCD have also overlooked thecompatibility between frame materials and the glass, for example, of theLCD. A rigid plastic frame, for example, has a different coefficient ofthermal expansion compared to glass and may cause the LCD glass to breakunder extremes of temperature Accordingly, operation over relativelywide temperature ranges may require complicated mounting techniques orthe effective operating temperature may be restricted. In addition,attempting to isolate the glass from the frame may increase difficultieswith shock and vibration.

SUMMARY OF THE INVENTION

In view of the foregoing background, it is therefore an object of thepresent invention to provide an LCD which is resistant to high shock andvibration levels.

It is another object of the present invention to provide an LCD which isreadily mounted while taking into account compatibility of the framematerial and the LCD materials.

These and other objects, advantages and features of the presentinvention are provided by an LCD including a first panel assembly and asecond panel assembly with a liquid crystal material layer positionedtherebetween, and wherein the first panel assembly has a resonantfrequency substantially the same as a resonant frequency of the secondpanel assembly so that the LCD is resistant to damage from shock andvibration. The first panel assembly preferably comprises a first coverpanel immediately adjacent the liquid crystal material layer and atleast one additional panel positioned adjacent the first cover panel.Similarly, the second panel assembly may comprise a second cover panelimmediately adjacent the layer of liquid crystal material and at leastone additional panel adjacent the second cover panel. In other words, atypical LCD sandwich including the first and second cover panels withthe liquid crystal material layer therebetween, further includes one ormore additional support panels.

Considered in different terms, the first panel assembly hassubstantially matched mechanical properties to the second panelassembly. For example, the substantially matched mechanical propertiespreferably include a stiffness to mass ratio. In addition, the resonantfrequency is preferably a first mode resonant frequency. Accordingly,damage caused by the relative motion between the first and secondassemblies is avoided by matching the first and second assemblies sothat they may move together.

For additional resistance to shocks, each of the assemblies may includea support panel, such as provided by an additional glass plate. A frontassembly, may also include at least one filter panel or plate.

Another aspect of the invention relates to a frame mounted around aperiphery of the first and second panel assemblies. Preferably, thefirst panel assembly has a coefficient of thermal expansionsubstantially the same as a coefficient of thermal expansion of thesecond panel assembly. For additional compatibility, the frame alsopreferably has a coefficient of thermal expansion substantially the sameas the coefficient of thermal expansion of the first and second panelassemblies.

A method aspect of the invention is for making a liquid crystal display(LCD) resistant to damage from vibration. The liquid crystal display ispreferably of a type including a liquid crystal material layerpositioned between two cover panels. The method preferably comprises thestep of positioning at least one additional panel adjacent at least onecover panel to define first and second panel assemblies on oppositesides of the liquid crystal material layer so that the first panelassembly has a resonant frequency substantially the same as a resonantfrequency of the second panel assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective view of an LCD in accordance with thepresent invention.

FIG. 2 is an exploded perspective view of a portion of the LCD in FIG.1.

FIG. 3 is a greatly enlarged side cross-sectional view of a portion ofthe LCD in FIG. 1.

FIG. 4 is an enlarged side cross-sectional view of a portion of anotherembodiment of an LCD in accordance with the present invention and asexplained in the example.

FIG. 5 is a graph illustrating glass thickness versus frequency for afront panel assembly as described in the example.

FIG. 6 is a graph illustrating glass deflection versus glass stackthickness for the front panel assembly as described in the example.

FIG. 7 is a graph illustrating bending stress as a function of glassthickness for the front panel assembly as described in the example.

FIG. 8 is a graph illustrating glass thickness versus frequency for arear panel assembly described in the example.

FIG. 9 is a graph illustrating glass deflection versus glass stackthickness for the rear panel assembly described in the example.

FIG. 10 is a graph illustrating bending stress as a function of glassthickness for the rear panel assembly described in the example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout The thickness of variouslayers may be exaggerated for clarity.

Referring initially to FIGS. 1-3, a first embodiment of an LCD 15 inaccordance with the present invention is now described. The LCD 15 mayused to display images 36 and/or text 37, for example, under computercontrol as would be readily understood by those skilled in the art. TheLCD 15 includes a plurality of stacked panels and a frame 30. The LCD 15may be used in many environments, such as aircraft and other vehicles,for example, which may subject the LCD to severe shocks and vibration.The present LCD is directed to being more resistant to such extremeconditions as described in greater detail below.

The frame 30 illustratively includes a body portion 30 a which surroundsthe periphery of the stacked panels, and a flange or mounting portion 30b which extends outwardly from a bottom portion of the body. Of course,those of skill in the art will appreciate many other configurations forthe frame 30 and especially the flange or mounting portion 30 b. Asshown in the enlarged cross-sectional view of FIG. 2, a relatively thickadhesive layer 33, such as an RTV compound or material, may be used toseal the stacked panels in the U-shaped channel defined by the bodyportion 30 a of the frame 30. The RTV is desirably not so thick as tosubject the LCD to further vibration effects. In addition, as also shownin FIG. 2, one or more mounting openings 31 may be provided in theflange portion 30 b to facilitate mounting via suitable fasteners.

The LCD 15 includes in stacked relation: an enhancement filter 16, asecond enhancement filter 17, a polarizer 18, and a first cover panel 19collectively defining a first or front panel assembly 40 (FIG. 2). Theliquid crystal material layer 20 is immediately adjacent the first coverpanel 19 of the front panel assembly 40. The second or rear panelassembly 41 includes the second cover panel 23, the second polarizer 24,and a support glass panel 25. An adhesive, not shown, is used to bondthe interfaces between certain of the adjacent panels as would bereadily understood by those skilled in the art.

The present invention recognizes that to reduce the potentially damagingeffects of shock and vibration, the front and rear panel assemblies 40,41 should be matched in terms of resonant frequency. In other words, thestiffness to mass ratio of the front panel assembly 40 matches that ofthe rear panel assembly 41.

Thus, the LCD 15 becomes much more resistant to shock and vibration. Asthe front panel assembly 40 is typically defined by the applicationdependent filters as shown in the illustrated embodiment, the supportglass panel 25 of the rear assembly 41 can be selected and tailored sothat the front and back assemblies match. Of course, in otherembodiments, support glass plates could be added to both the front andrear assemblies or just the front assembly as would be readilyappreciated by those skilled in the art, as long as the assembliesmatched in terms of stiffness to mass ratio to thereby match theresonant frequencies.

Considered in somewhat different terms, the front or first panelassembly 40 has substantially matched mechanical properties to thesecond or rear panel assembly 41. For example, the substantially matchedmechanical properties preferably include, for example, the stiffness tomass ratio. In addition, the resonant frequency is preferably a firstmode resonant frequency. Accordingly, damage potentially caused by therelative motion between the first and second assemblies 40, 41 isavoided by matching the resonant frequencies of the first and secondassemblies.

Another aspect of the invention relates to the material and propertiesof the LCD mounting frame 30. Preferably, the front panel assembly 40has a coefficient of thermal expansion substantially the same as acoefficient of thermal expansion of the rear panel assembly 41, which istypically the case since both include primarily glass For additionalcompatibility, the frame 30 also preferably has a coefficient of thermalexpansion substantially the same as the coefficient of thermal expansionof the first and second panel assemblies. As would be readily understoodby those skilled in the art, the temperature range of interest may befrom −65° to 185° F.

For example, the coefficient of thermal expansion for glass is about 2.6to 6.2 in/(in)(° F.)×10⁻⁶, and may typically be about 3.0 in/(in)(°F.)×10⁻⁶ for an LCD. Unfortunately, aluminum, which is relativelylightweight and strong, has a relatively high coefficient of thermalexpansion in a range of about 12.6 to 13.7 in/(in)(° F.)×10⁻⁶. In oneembodiment of the present invention, the frame 30 preferably includestitanium which has a coefficient of thermal expansion of about 5.2in/(in)(° F.)×10⁻⁶. Titanium is both lightweight and relatively strong,which makes it highly desirable for the present application. Othermaterials and composites, for example, may also be used that have asimilar compatible coefficient of thermal expansion.

A method aspect of the invention is for making an LCD 15 as describedabove. The LCD 15 is preferably of a type including a liquid crystalmaterial layer positioned between two cover panels. The methodpreferably comprises the step of positioning at least one additionalpanel 25 adjacent at least one cover panel to define first and secondpanel assemblies 40, 41 on opposite sides of the liquid crystal materiallayer 20 so that the first panel assembly has a resonant frequencysubstantially the same as a resonant frequency of the second panelassembly.

EXAMPLE

The description is now directed to an example illustrating determinationof the matching properties of the front and rear panel assemblies for anembodiment of an LCD 45 as shown in the cross-sectional view of FIG. 4.This embodiment includes a front panel assembly 46 comprising in stackedrelation: a first front borosilicate glass panel 50, a filter panel 51,a second front borosilicate glass panel 52, a front polarizer 53, andthe front cover glass panel 54. The rear panel assembly includes instacked relation: a first rear borosilicate glass panel 58, a secondrear borosilicate glass panel 57 (optional), a rear polarizer 56, andthe rear glass cover panel 55B. The liquid crystal material layer 71 isbetween the front and rear assemblies 46, 47. As would be readilyunderstood by those skilled in the art, various epoxy bond layers, notshown, are positioned between the adjacent panels.

The LCD 45 includes a frame 60 including a body portion 60 a and aflange portion 60 b. A layer of sealing material 60 is in the U-shapedchannel defined by the body portion 60 a. Openings 62 may be provided tomount the LCD using suitable fasteners.

In this example, the front panel assembly 46 is first considered, thenthe rear panel assembly 47 is considered. The rear assembly glass isdetermined to match the resonant frequency of the front glass panelassembly. This further description assumes the inner and outer surfacesof the LCD act independent of each other from a structural stiffnessview point. Therefore only one surface is considered. In general, thevibration frequencies of interest are in the range of about 5 Hz to 2KHz.

Based upon the following parameters, a relationship between the frontassembly thickness and its resonant frequency can be determined asfollows:

μ = 0.25 Poisson's Ratio E₁ = 9.2 · 10⁶ psi Modulus of Elast. Layer #1(borosilicate glass) E₂ = 0.5 · 10⁶ psi Modulus of Elast. Layer #2(epoxy) E₃ = 9.4 · 10⁶ psi Modulus of Elast. Layer #3 (TN abs. glass) E₄= 0.5 · 10⁶ psi Modulus of Elast. Layer #4 (epoxy) E₅ = 9.2 · 10⁶ psiModulus of Elast. Layer #5 (borosilicate glass) E₆ = 0.5 · 10⁶ psiModulus of Elast. Layer #6 (polarizer) E₇ = 10.1 · 10⁶ psi Modulus ofElast. Layer #7 (LCD, Corning 1737F) b = 8.54 in Glass Unsupported Widtha = 6.30 in Glass Unsupported Length W_(c) = 0.00 lb Est. Non-StructuralWeight Supported by Glass t₁ = 0.040 in Thickness of Layer #1 t₂ = 0.001in Thickness of Layer #2 t₃ = 0.040 in Thickness of Layer #3 t₄ = 0.001in Thickness of Layer #4 t₅ = 0.0 in Initial Thickness of Layer #5t_(5i) = t_(5+i·z) Variable Thickness of Layer #5 t₆ = 0.009 inThickness of Layer #6 t₇ = 0.045 in Thickness of Layer #7 ρ₁ = 0.0775lb/in³ Density of Layer #1 ρ₂ = 0.055 lb/in³ Density of Layer #2 ρ₃ =0.1264 lb/in³ Density of Layer #3 ρ₄ = 0.055 lb/in³ Density of Layer #4ρ₅ = 0.0775 lb/in³ Density of Layer #5 ρ₆ = 0.055 lb/in³ Density ofLayer #6 ρ₇ = 0.0775 lb/in³ Density of Layer #7 W₁ = a · b · t₁ · ρ₁Weight of Layer #1 W₂ = a · b · t₂ · ρ₂ Weight of Layer #2 W₃ = a · b ·t₃ · ρ₃ Weight of Layer #3 W₄ = a · b · t₄ · ρ₄ Weight of Layer #4 W₄ =a · b · t₅ · ρ_(5i) Weight of Layer #5 W₆ = a · b · t₆ · ρ₆ Weight ofLayer #6 W₇ = a · b · t₇ · ρ₇ Weight of Layer #7 h_(ri) = t₁ + t₂ + t₃ +t₄ + t_(5i) + t₆ + t₇ Assembly Variable Thickness W_(ti) = W₁ + W₂ +W₃ + W₄ + W_(5i) + Display Glass Total Weight W₆ + W₇ A₁ = b · t₁ Layer#1 Cross Sectional Area A₂ = b · t₂ Layer #2 Cross Sectional Area A₃ = b· t₃ Layer #3 Cross Sectional Area A₄ = b · t₄ Layer #4 Cross SectionalArea A_(5i) = b · t_(5i) Layer #5 Cross Sectional Area A₆ = b · t₆ Layer#6 Cross Sectional Area A₇ = b · t₇ Layer #7 Cross Sectional Area

The distance from Layer #1 surface to neutral axis can be found from:$\begin{matrix}{Z_{i} = \frac{\begin{bmatrix}{{A_{1} \cdot E_{1} \cdot \frac{t_{1}}{2}} + {A_{2} \cdot E_{2} \cdot \left( {t_{1} + \frac{t_{2}}{2}} \right)} + {A_{3} \cdot E_{3} \cdot \left( {t_{1} + t_{2} + \frac{t_{3}}{2}} \right)} +} \\{{{A_{4} \cdot E_{4} \cdot \left( {t_{1} + t_{2} + t_{3} + \frac{t_{4}}{2}} \right)}\quad \ldots} + {A_{5_{i}} \cdot E_{5} \cdot \left( {t_{1} + t_{2} + t_{3} + t_{4} + \frac{t_{5_{i}}}{2}} \right)} +} \\{{{A_{6} \cdot E_{6} \cdot \left( {t_{1} + t_{2} + t_{3} + t_{4} + t_{5_{i}} + \frac{t_{6}}{2}} \right)}\quad \ldots} + {A_{7} \cdot E_{7} \cdot \left( {t_{1} + t_{2} + t_{3} + t_{4} + t_{5_{i}} + t_{6} + \frac{t_{7}}{2}} \right)}}\end{bmatrix}}{{A_{1} \cdot E_{1}} + {A_{2} \cdot E_{2}} + {A_{3} \cdot E_{3}} + {A_{4} \cdot E_{4}} + {A_{5_{i}} \cdot E_{5}} + {A_{6} \cdot E_{6}} + {A_{7} \cdot E_{7}}}} \\\begin{matrix}{c_{1i} = {Z_{i} - {{t_{1}/2}\quad \text{~~~~~~~~~~~~~~~~~~~~~~}\quad {Distance}\quad {from}\quad {Layer}\quad {\# 1}\quad {centroid}\quad {to}\quad {Neutral}\quad {Axis}}}} \\{c_{2i} = {Z_{i} - {\left( {t_{1} + {t_{2}/2}} \right)\text{~~~~~}{Distance}\quad {from}\quad {Layer}\quad {\# 2}\quad {centroid}\quad {to}\quad {Neutral}\quad {Axis}}}} \\{c_{3i} = {Z_{i} - {\left( {t_{1} + t_{2} + {t_{3}/2}} \right)\text{~~~~~~}{Distance}\quad {from}\quad {Layer}\quad {\# 3}\quad {centroid}\quad {to}\quad {Neutral}\quad {Axis}}}} \\{c_{4i} = {Z_{i} - {\left( {t_{1} + t_{2} + t_{3} + t_{4}} \right)\text{~~~~}{{Dist}.\quad {Layer}}\quad {\# 4}\quad {centroid}\quad {to}\quad {{Neut}.\quad {Axis}}}}} \\{c_{5i} = {Z_{i} - {\left( {t_{1} + t_{2} + t_{3} + t_{4} + {t_{5i}/2}} \right)\quad \text{~~~~~~~~~~~~~~~~}{{Dist}.\quad {Layer}}\quad {\# 5}\quad {centroid}\quad {to}\quad {{Neut}.\quad {Axis}}}}} \\{c_{6i} = {Z_{i} - {\left( {t_{1} + t_{2} + t_{3} + t_{4} + t_{5i} + {t_{6}/2}} \right)\text{~~~~~~~~~}{{Dist}.\quad {Layer}}\quad {\# 6}\quad {centroid}\quad {to}\quad {{Neut}.\quad {Axis}}}}} \\{c_{7i} = {Z_{i} - {\left( {t_{1} + t_{2} + t_{3} + t_{4} + t_{5i} + t_{6} + {t_{7}/2}} \right)\text{~~}{{Dist}.\quad {Layer}}\quad {\# 7}\quad {centroid}\quad {to}\quad {{Neut}.\quad {Axis}}}}}\end{matrix} \\\begin{matrix}{S_{e} = {100\%}} & {{Shear}\quad {Efficiency}} \\{S_{pol} = {65\%}} & {{Shear}\quad {Efficiency}} \\{I_{1} = {b \cdot {t_{1}^{3}/12}}} & {{Area}\quad {Moment}\quad {of}\quad {Inertia}\quad {of}\quad {Layers}\quad {\# 1}\text{-}{\# 7}} \\{I_{2} = {b \cdot {t_{2}^{3}/12}}} & \quad \\{I_{3} = {b \cdot {t_{3}^{3}/12}}} & \quad \\{I_{4} = {b \cdot {t_{4}^{3}/12}}} & \quad \\{I_{5} = {b \cdot {t_{5}^{3}/12}}} & \quad \\{I_{6} = {b \cdot {t_{6}^{3}/12}}} & \quad \\{I_{7} = {b \cdot {t_{7}^{3}/12}}} & \quad \\{I_{T1i} = {I_{1} + {S_{e} \cdot A_{1} \cdot \left( c_{1i} \right)^{2}}}} & {{Area}\quad {Moment}\quad {of}\quad {Inertia}\quad {of}\quad {Layers}\quad {\# 1}\quad {to}\quad {\# 7}} \\\quad & {{About}\quad {the}\quad {Composite}\quad {Neutral}\quad {Axis}} \\{I_{T2i} = {I_{2} + {S_{e} \cdot A_{2} \cdot \left( c_{2i} \right)^{2}}}} & \quad \\{I_{T3i} = {I_{3} + {S_{e} \cdot A_{3} \cdot \left( c_{3i} \right)^{2}}}} & \quad \\{I_{T4i} = {I_{4} + {S_{e} \cdot A_{4} \cdot \left( c_{4i} \right)^{2}}}} & \quad \\{I_{T5i} = {I_{5i} + {S_{e} \cdot A_{5i} \cdot \left( c_{5i} \right)^{2}}}} & \quad \\{I_{T6i} = {I_{6} + {S_{e} \cdot A_{6} \cdot \left( c_{6i} \right)^{2}}}} & \quad \\{I_{T7i} = {I_{7} + {S_{e} \cdot A_{7} \cdot \left( c_{7i} \right)^{2}}}} & \quad\end{matrix}\end{matrix}$

Accordingly, the equivalent area moment of inertia is given by:$I_{{eq}_{i}} = \frac{b \cdot \left( {t_{1} + t_{2} + t_{3} + t_{4} + t_{5_{i}} + t_{6} + t_{7}} \right)^{3}}{12}$

and the equivalent modulus of elasticity is given by:$e_{{qe}_{i}} = \frac{\begin{matrix}{{E_{1} \cdot I_{{T1}_{i}}} + {E_{2} \cdot I_{{T2}_{i}}} + {E_{3} \cdot I_{{T3}_{i}}} + {E_{4} \cdot I_{{T4}_{i}}} +} \\{{E_{5} \cdot I_{{T5}_{i}}} + {E_{6} \cdot I_{{T6}_{i}}} + {E_{7} \cdot I_{T7}}}\end{matrix}}{I_{{eq}_{i}}}$

Moreover, the edge simple support is as follows:${f1}_{2_{i}} = {\left( {\frac{1}{a^{2}} + \frac{1}{b^{2}}} \right) \cdot \left\lbrack \sqrt{\frac{\frac{\frac{E_{{eq}_{i}} \cdot \left( h_{r_{i}} \right)^{3}}{12 \cdot \left( {1 - \mu^{2}} \right)}}{{Wt}_{i}}}{a \cdot b}} \right\rbrack \cdot \left( \frac{\pi}{2} \right)}$

The plot labeled 70 of FIG. 5 illustrates the relationship of displaythickness versus resonant frequency. of interest, for a thickness of0.164 in shown by dotted vertical line 72, the corresponding frequencyis indicated by the intersection with the dotted horizontal line 73 at553 Hz. The resonant frequencies for other thickness may be readilydetermined from the graph as would be appreciated by those skilled inthe art.

Continuing the analysis, the amount of glass deflection may also bereadily determined as follows.

ζ = 4.4% Estimated Structural Damping Q = ½ · ζ Estimated AmplificationBased Upon Damping PSD = 0.31/Hz Estimated Power Spectral DensityG_(sdof) _(i) = (π/2 · PSD · Q · f1₂ _(i) )^(.5) Equiv. Single Deg.Freedom “G” Level

Accordingly, the glass stack deflection versus resonant frequency isfound by:$\delta_{i} = \frac{G_{{sdof}_{i}} \cdot g}{4 \cdot \pi^{2} \cdot \left( {f1}_{2_{i}} \right)^{2}}$

A graphical plot labeled 75 for the display deflection versus frontassembly thickness is shown in FIG. 6. The vertical dotted line 76represents a thickness of 0.164 inches, and as can be seen, intersectsthe plot at the horizontal dashed line 77 indicated that the deflectionwould be 0.00177 in. This amount of deflection was determined to beacceptable in view of a threshold of lower than about 0.002 inches

The plate deflection and stress with a uniform load is determined asfollows:

r_(r) = b/a aspect ratio j = 1..10 r_(j) = .1 · (j − 1) r_(j) = β_(j) =1 0.2874 vs = csplin (r, β) 1.2 0.3762 1.4 0.4530 interp (vs, r, β,r_(r)) = 0.5 1.6 0.5172 1.8 0.5688 2 0.6102 3 0.7134 4 0.7410 5 0.7476100 0.750$\sigma_{i} = \frac{{{interp}\left( {{vs},r,\beta,r_{r}} \right)} \cdot \frac{{Wt}_{i} \cdot G_{{sdof}_{i}} \cdot g}{a \cdot b} \cdot a^{2}}{\left( h_{r_{i}} \right)^{2}}$

The bending stress as a function of the glass thickness based upon theabove is shown by the plot 80 of FIG. 7. In particular, the verticalline 81 is for the thickness of 0.164 as used in this example. Thevertical line 81 intersects the horizontal line 82 indicated that astress of 516 would be experienced. This level is well below stresseswhich may damage the glass as would be readily appreciated by thoseskilled in the art.

Having now determined the various workable parameters for the frontpanel assembly 46, the analysis may now turn to ensuring matching of therear panel assembly 47 as given below.

μ = 0.25 Poisson's Ratio E₁ = 9.2 · 10⁶ psi Modulus of Elast. Layer #1(borosilicate glass) E₂ = 0.5 · 10⁶ psi Modulus of Elast. Layer #2(epoxy) E₃ = 9.2 · 10⁶ psi Modulus of Elast. Layer #3 (borosilicateglass) E₄ = 0.1 · 10⁶ psi Modulus of Elast. Layer #4 (polarizer) E₅ =10.1 · 10⁶ psi Modulus of Elast. Layer #5 (LCD, Corning 1737F) t₁ =0.070 · in Initial Thickness of Layer #1 t_(1i) = t_(1+i·z) VariableThickness of Layer #1 t₂ = 0.001 in Thickness of Layer #2 t₃ = 0.00 inThickness of Layer #3 t₄ = 0.008 in Thickness of Layer #4 t₅ = 0.045 inThickness of Layer #5 ρ₁ = 0.0775 lb/in³ Density of Layer #1 ρ₂ = 0.055lb/in³ Density of Layer #2 ρ₃ = 0.0775 lb/in³ Density of Layer #3 ρ₄ =0.055 lb/in³ Density of Layer #4 ρ₅ = 0.0775 lb/in³ Density of Layer #5W_(1i) = a · b · t_(1i)ρ₁ Weight of Layer #1 W₂ = a · b · t₂ · ρ₂ Weightof Layer #2 W₃ = a · b · t₃ · ρ₃ Weight of Layer #3 W₄ = a · b · t₄ · ρ₄Weight of Layer #4 W₅ = a · b · t₅ · ρ₅ Weight of Layer #5 h_(r) _(i) =t₁ _(i) + t₂ + t₃ + t₄ + t₅ Assembly Variable Thickness Wt_(i) = W₁_(i) + W₂ + W₃ + W₄ + W₅ Display Glass Total Weight A_(1i) = b · t_(1i)Layer #1 Cross Sectional Area A₂ = b · t₂ Layer #2 Cross Sectional AreaA₃ = b · t₃ Layer #3 Cross Sectional Area A₄ = b · t₄ Layer #4 CrossSectional Area A₅ = b · t₅ Layer #5 Cross Sectional Area

Accordingly, the distance from Layer #1 Surface to Neutral Axis is givenby: $\begin{matrix}{Z_{i} = \frac{\begin{bmatrix}{{A_{1_{i}} \cdot E_{1} \cdot \frac{t_{1_{i}}}{2}} + {A_{2} \cdot E_{2} \cdot \left( {t_{1_{i}} + \frac{t_{2}}{2}} \right)} + {A_{3} \cdot E_{3} \cdot \left( {t_{1_{i}} + t_{2} + \frac{t_{3}}{2}} \right)} +} \\{{{A_{4} \cdot E_{4} \cdot \left( {t_{1_{i}} + t_{2} + t_{3} + \frac{t_{4}}{2}} \right)}\quad \ldots} + {A_{5} \cdot E_{5} \cdot \left( {t_{1_{i}} + t_{2} + t_{3} + t_{4} + \frac{t_{5_{i}}}{2}} \right)}}\end{bmatrix}}{{A_{1_{i}} \cdot E_{1}} + {A_{2} \cdot E_{2}} + {A_{3} \cdot E_{3}} + {A_{4} \cdot E_{4}} + {A_{5} \cdot {E5}}}} \\\begin{matrix}{c_{1_{i}} = {Z_{i} - {{t_{1_{i}}/2}\quad \text{~~~~~~~~~~~~~~~~~~~~}\quad {Distance}\quad {from}\quad {Layer}\quad {\# 1}\quad {centroid}\quad {to}\quad {Neutral}\quad {Axis}}}} \\{c_{2_{i}} = {Z_{i} - {\left( {t_{1_{i}} + {t_{2}/2}} \right){\quad\text{~~}}\quad {Distance}\quad {from}\quad {Layer}\quad {\# 2}\quad {centroid}\quad {to}\quad {Neutral}\quad {Axis}}}} \\{c_{3_{i}} = {Z_{i} - {\left( {t_{1_{i}} + t_{2} + {t_{3}/2}} \right)\text{~~~~~}\quad {Layer}\quad {\# 3}\quad {centroid}\quad {to}\quad {Neutral}\quad {Axis}}}} \\{c_{4_{i}} = {Z_{i} - {\left( {t_{1_{i}} + t_{2} + t_{3} + t_{4}} \right)\text{~~~}{Layer}\quad {\# 4}\quad {centroid}\quad {to}\quad {{Neut}.\quad {Axis}}}}} \\{c_{5_{i}} = {Z_{i} - {\left( {t_{1_{i}} + t_{2} + t_{3} + t_{4} + {t_{5}/2}} \right)\quad \text{~~}\quad {Layer}\quad {\# 5}\quad {centroid}\quad {to}\quad {{Neut}.\quad {Axis}}}}}\end{matrix} \\\begin{matrix}{S_{e} = {100\%}} & {{Shear}\quad {Efficiency}} \\{S_{pol} = {65\%}} & {{Shear}\quad {Efficiency}\quad {of}\quad {Polarizer}} \\{I_{1_{i}} = {b \cdot {\left( t_{1_{i}} \right)^{3}/12}}} & {{Area}\quad {Moment}\quad {of}\quad {Inertia}\quad {of}\quad {Layers}\quad {\# 1}\text{-}{\# 7}} \\{I_{2} = {b \cdot {t_{2}^{3}/12}}} & \quad \\{I_{3} = {b \cdot {t_{3}^{3}/12}}} & \quad \\{I_{4} = {b \cdot {t_{4}^{3}/12}}} & \quad \\{I_{5} = {b \cdot {\left( t_{5} \right)^{3}/12}}} & \quad \\{I_{{T1}_{i}} = {I_{1_{i}} + {S_{e} \cdot A_{1_{i}} \cdot \left( c_{1_{i}} \right)^{2}}}} & {{Area}\quad {Moment}\quad {of}\quad {Inertia}\quad {of}\quad {Layers}\quad {\# 1}\text{-}{\# 5}} \\\quad & {{About}\quad {the}\quad {Composite}\quad {Neutral}\quad {Axis}} \\{I_{{T2}_{i}} = {I_{2} + {S_{e} \cdot A_{2} \cdot \left( c_{2_{i}} \right)^{2}}}} & \quad \\{I_{{T3}_{i}} = {I_{3} + {S_{e} \cdot A_{3} \cdot \left( c_{3_{i}} \right)^{2}}}} & \quad \\{I_{{T4}_{i}} = {I_{4} + {S_{pol} \cdot A_{4} \cdot \left( c_{4i} \right)^{2}}}} & \quad \\{I_{{T5}_{i}} = {I_{5} + {S_{pol} \cdot A_{5} \cdot \left( c_{5_{i}} \right)^{2}}}} & \quad\end{matrix}\end{matrix}$

Accordingly, the equivalent area moment of inertia is given by:

I _(eq) _(i) =b·(t ₁ _(i) +t ₂ +t ₃ +t ₄ +t ₅)³/12

And the equivalent modulus of elasticity is given by:

E _(eq) _(i) =(E ₁ ·I _(T1) _(i) +E ₂ ·I _(T2) _(i) +E ₃ ·I _(T3) _(i)+E ₄ ·I _(T4) _(i) +E ₅ ·I _(T5) _(i) )/I _(eqi)

Moreover, the edge simple support is as follows:${f1}_{2_{i}} = {\left( {\frac{1}{a^{2}} + \frac{1}{b^{2}}} \right) \cdot \left\lbrack \sqrt{\frac{\frac{\frac{E_{{eq}_{i}} \cdot \left( h_{r_{i}} \right)^{3}}{12 \cdot \left( {1 - \mu^{2}} \right)}}{{Wt}_{i}}}{a \cdot b}} \right\rbrack \cdot \left( \frac{\pi}{2} \right)}$

The plot labeled 85 of FIG. 8 illustrates this relationship of displaythickness versus resonant frequency for the rear panel assembly 47. Ofinterest, for a thickness of 0.0152 in shown by the dotted vertical line86, the corresponding frequency is indicated by the intersection withthe dotted horizontal line 87 at 553 Hz, and this is the frequencycalculated for the front panel assembly 46 above. In other words, inthis example, the rear panel assembly should have a thickness of 0.164in to match the resonant frequency, 533 Hz of the front patent assembly.

Continuing the analysis, the amount of glass deflection may also bereadily determined as follows.

ζ = 4.4% Estimated Structural Damping Q = ½ · ζ Estimated AmplificationBased Upon Damping PSD = 0.31/Hz Estimated Power Spectral DensityG_(sdof) _(i) = (π/2 · PSD · Q · f1₂ _(i) )^(.5) Equiv. Single Deg. ofFree. “G”

The glass stack defection as a function of the resonant frequency isgiven by:$\delta_{i} = \frac{G_{{sdof}_{i}} \cdot g}{4 \cdot \pi^{2} \cdot \left( {f1}_{2_{i}} \right)^{2}}$

A graphical plot labeled 90 for the display deflection versus frontassembly thickness is shown in FIG. 9. The vertical dotted line 91represents a thickness of 0.152 inches, and as can be seen, intersectsthe plot at the horizontal dashed line 92 indicated that the deflectionwould be 0.00177 in. This amount of deflection was determined to beacceptable in view of a threshold of lower than about 0.002 inches.

The stress based upon the thickness under a uniform load may also becalculated as follows.

r_(r) = b/a Plate aspect ratio j = 1..10 r_(j) = .1 · (j − 1) r_(j) =β_(j) = 1 0.2874 vs = csplin (r, β) 1.2 0.3762 1.4 0.4530 interp (vs, r,β, r_(r)) = 0.5 1.6 0.5172 1.8 0.5688 2 0.6102 3 0.7134 4 0.7410 50.7476 100 0.750$a_{i} = \frac{{{interp}\left( {{vs},r,\beta,r_{r}} \right)} \cdot \frac{{WT}_{i} \cdot G_{{sdof}_{i}} \cdot g}{a \cdot b} \cdot a^{2}}{\left( h_{r_{i}} \right)^{2}}$

The bending stress as a function of the glass thickness is shown by theplot 95 of FIG. 10. In particular, the vertical line 96 is for thethickness of 0.152 as used in rear panel assembly 47 in this example.The vertical line 96 intersects the horizontal line 97 indicated that astress of 481 would be experienced. This level is well below stresseswhich may damage the glass as would be readily appreciated by thoseskilled in the art.

Many modifications and other embodiments of the invention will come tothe mind of one skilled in the art having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is to be understood that the invention is not to belimited to the specific embodiments disclosed, and that modificationsand embodiments are intended to be included within the scope of theappended claims.

That which is claimed is:
 1. A liquid crystal display (LCD) beingresistant to damage from shock and vibration and comprising: a firstpanel assembly and a second panel assembly having differentconstructions; a liquid crystal material layer positioned between saidfirst and second panel assemblies; said first panel assembly comprisinga first cover panel immediately adjacent said liquid crystal materiallayer and at least one additional panel positioned adjacent said firstcover panel; said second assembly comprising a second cover panelimmediately adjacent said layer of liquid crystal material and at leastone additional panel adjacent said second cover panel; said first panelassembly having a resonant frequency substantially the same as aresonant frequency of said second panel assembly despite said first andsecond panel assemblies having different constructions and so that theLCD is resistant to damage from shock and vibration.
 2. An LCD accordingto claim 1 wherein said first panel assembly has substantially matchedmechanical properties to said second panel assembly.
 3. An LCD accordingto claim 2 wherein the substantially matched mechanical propertiesinclude a stiffness to mass ratio.
 4. An LCD according to claim 1wherein said resonant frequency is a first mode resonant frequency. 5.An LCD according to claim 1 wherein the at least one additional panel ofsaid first panel assembly comprises a support panel.
 6. An LCD accordingto claim 5 wherein said support panel comprises a glass plate.
 7. An LCDaccording to claim 1 wherein the at least one additional panel of saidsecond panel assembly comprises at least one filter panel.
 8. An LCDaccording to claim 1 wherein the at least one additional panel of saidsecond panel assembly comprises a support panel.
 9. An LCD according toclaim 8 wherein said support panel comprises a glass plate.
 10. An LCDaccording to claim 1 further comprising a frame mounted around aperiphery of said first and second panel assemblies.
 11. An LCDaccording to claim 10 wherein said first panel assembly has acoefficient of thermal expansion substantially the same as a coefficientof thermal expansion of said second panel assembly; and wherein saidframe has a coefficient of thermal expansion substantially the same asthe coefficient of thermal expansion of said first and second panelassemblies.
 12. An LCD according to claim 11 wherein said first andsecond panel assemblies comprise glass; and wherein said frame comprisestitanium.
 13. An LCD according to claim 1 wherein at least one of saidfirst and second panel assemblies further comprises a polarizer.
 14. AnLCD according to claim 1 wherein said first and second panel assemblieshave different thicknesses.
 15. An LCD according to claim 1 wherein saidfirst and second panel assemblies comprise respective panels having atleast one different characteristic.
 16. An LCD according to claim 15wherein said at least one different characteristic comprises at leastone of different module of elasticity and densities.
 17. A liquidcrystal display (LCD) comprising: a first panel assembly and a secondpanel assembly having different constructions; a liquid crystal materiallayer positioned between said first and second panel assemblies; saidfirst panel assembly comprising a first cover panel immediately adjacentsaid liquid crystal material layer and a support panel positionedadjacent said first cover panel; said second assembly comprising asecond cover panel immediately adjacent said layer of liquid crystalmaterial; said first panel assembly having a resonant frequencysubstantially the same as a resonant frequency of said second panelassembly despite said first and second panel assemblies having differentconstructions.
 18. An LCD according to claim 17 wherein said first panelassembly has substantially matched mechanical properties to said secondpanel assembly.
 19. An LCD according to claim 18 wherein thesubstantially matched mechanical properties include a stiffness to massratio.
 20. An LCD according to claim 17 wherein said resonant frequencyis a first mode resonant frequency.
 21. An LCD according to claim 17wherein said support panel comprises a glass plate.
 22. An LCD accordingto claim 17 wherein said second panel assembly further comprises atleast one filter panel.
 23. An LCD according to claim 17 wherein saidsecond panel assembly further comprises a support panel.
 24. An LCDaccording to claim 23 wherein said support panel comprises a glassplate.
 25. An LCD according to claim 17 further comprising a framemounted around a periphery of said first and second panel assemblies.26. An LCD according to claim 25 wherein said first panel assembly has acoefficient of thermal expansion substantially the same as a coefficientof thermal expansion of said second panel assembly; and wherein saidframe has a coefficient of thermal expansion substantially the same asthe coefficient of thermal expansion of said first and second panelassemblies.
 27. An LCD according to claim 26 wherein said first andsecond panel assemblies comprise glass; and wherein said frame comprisestitanium.
 28. An LCD according to claim 17 wherein at least one of saidfirst and second panel assemblies further comprises a polarizer.
 29. AnLCD according to claim 17 wherein said first and second panel assemblieshave different thicknesses.
 30. An LCD according to claim 17 whereinsaid first and second panel assemblies comprise respective panels havingat least one different characteristic.
 31. An LCD according to claim 30wherein said at least one different characteristic comprises at leastone of different module of elasticity and densities.
 32. A liquidcrystal display (LCD) comprising: a first panel assembly and a secondpanel assembly having different constructions; and a liquid crystalmaterial layer positioned between said first and second panelassemblies; said first panel assembly having a stiffness to mass ratiosubstantially the same as a stiffness to mass ratio of said second panelassembly despite said first and second panel assemblies having differentconstructions.
 33. An LCD according to claim 32 wherein said first panelassembly comprises a support panel.
 34. An LCD according to claim 33wherein said support panel comprises a glass plate.
 35. An LCD accordingto claim 32 wherein said second panel assembly comprises at least onefilter panel.
 36. An LCD according to claim 32 wherein said second panelassembly comprises a support panel.
 37. An LCD according to claim 36wherein said support panel comprises a glass plate.
 38. An LCD accordingto claim 32 further comprising a frame mounted around a periphery ofsaid first and second panel assemblies.
 39. An LCD according to claim 38wherein said first panel assembly has a coefficient of thermal expansionsubstantially the same as a coefficient of thermal expansion of saidsecond panel assembly; and wherein said frame has a coefficient ofthermal expansion substantially the same as the coefficient of thermalexpansion of said first and second panel assemblies.
 40. An LCDaccording to claim 32 wherein said first and second panel assemblieshave different thicknesses.
 41. An LCD according to claim 32 whereinsaid first and second panel assemblies comprise respective panels havingat least one different characteristic.
 42. An LCD according to claim 41wherein said at least one different characteristic comprises at leastone of different module of elasticity and densities.
 43. A method formaking a liquid crystal display (LCD) resistant to damage fromvibration, the liquid crystal display of a type including a liquidcrystal material layer positioned between two cover panels, the methodcomprising the step of: positioning at least one additional paneladjacent at least one cover panel of the two cover panels between whichthe liquid crystal material is positioned to define first and secondpanel assemblies having different constructions on opposite sides of theliquid crystal material layer but with the first panel assembly having aresonant frequency substantially the same as a resonant frequency of thesecond panel assembly despite the first and second panel assemblieshaving different constructions.
 44. A method according to claim 43further comprising the step of first forming the at least one additionalpanel so that the first panel assembly has substantially matchedmechanical properties to the second panel assembly.
 45. A methodaccording to claim 44 wherein the substantially matched mechanicalproperties include a stiffness to mass ratio.
 46. A method according toclaim 43 wherein the resonant frequency is a first mode resonantfrequency.
 47. A method according to claim 43 wherein the step ofpositioning at least one additional panel comprises positioning at leastone support panel.
 48. A method according to claim 47 wherein thesupport panel comprises a glass plate.
 49. A method according to claim43 further comprising the step of positioning a frame mounted around aperiphery of the first and second panel assemblies.
 50. A methodaccording to claim 49 wherein the first panel assembly has a coefficientof thermal expansion substantially the same as a coefficient of thermalexpansion of the second panel assembly; and wherein the step ofpositioning the frame comprises providing the frame having a coefficientof thermal expansion substantially the same as the coefficient ofthermal expansion of said first and second panel assemblies.
 51. Amethod for making a liquid crystal display (LCD) resistant to damagefrom vibration, the liquid crystal display of a type including a liquidcrystal material layer positioned between two cover panels, the methodcomprising the step of: positioning at least one additional paneladjacent at least one cover panel of the two cover panels between whichthe liquid crystal material is positioned to define first and secondpanel assemblies having different constructions on opposite sides of theliquid crystal material layer but with the first panel assembly having astiffness to mass ratio substantially the same as a stiffness to massratio of the second panel assembly despite the first and second panelassemblies having different constructions.
 52. A method according toclaim 51 wherein the step of positioning at least one additional panelcomprises positioning at least one support panel.
 53. A method accordingto claim 52 wherein the support panel comprises a glass plate.
 54. Amethod according to claim 51 further comprising the step of positioninga frame mounted around a periphery of the first and second panelassemblies.
 55. A method according to claim 54 wherein the first panelassembly has a coefficient of thermal expansion substantially the sameas a coefficient of thermal expansion of the second panel assembly; andwherein the step of positioning the frame comprises providing the framehaving a coefficient of thermal expansion substantially the same as thecoefficient of thermal expansion of said first and second panelassemblies.